Rotary power tool

ABSTRACT

A power tool includes a housing, a motor, a spindle, a handle holder and an auxiliary handle. The housing includes a motor housing portion, a drive housing, and a mounting portion between the motor housing portion and the drive housing. The motor is located within the motor housing portion. The spindle is configured to rotate about a rotational axis in response to torque received from the motor. The handle holder is coupled to the drive housing and defines a first mounting point, and the mounting portion defines a second mounting point. The auxiliary handle is selectively attachable to each of the first and second mounting points, and the first mounting point is located at a first position along the rotational axis, and the second mounting point is located at a second position offset from the first position in a direction along the rotational axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/050,044, filed Jul. 31, 2018, which claims priority to U.S.Provisional Patent Application No. 62/538,884, filed on Jul. 31, 2017,the entire content of both of which are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to rotary power tools, and moreparticularly to core drills.

BACKGROUND OF THE INVENTION

Core drills are typically used to remove a cylinder of material from aworkpiece.

SUMMARY OF THE INVENTION

The present invention provides, in one aspect, a rotary power toolincluding a housing having a motor housing portion, a drive housing, anda mounting portion between the motor housing portion and the drivehousing. The rotary power tool further includes a motor located withinthe motor housing portion, a spindle configured to rotate about arotational axis in response to torque received from the motor, and ahandle holder coupled to the drive housing. The handle holder defines afirst mounting point, and the mounting portion defines a second mountingpoint. An auxiliary handle is selectively attachable to each of thefirst and second mounting points. The first mounting point is located ata first position along the rotational axis, and the second mountingpoint is located at a second position offset from the first position ina direction along the rotational axis.

The present invention provides, in another aspect, a power toolincluding a housing with a motor housing portion, a drive housing, and amounting portion between the motor housing portion and the drivehousing, a motor located within the motor housing portion, a spindleconfigured to rotate about a rotational axis in response to torquereceived from the motor, and a transmission at least partially disposedwithin the drive housing. The transmission is configured to transmittorque from the motor to the spindle. The power tool also includes anauxiliary handle selectively attachable to the housing at each of afirst mounting point, a second mounting point, and a third mountingpoint. At least one of the group consisting of the first mounting point,the second mounting point, and the third mounting point is located onthe mounting portion.

The present invention provides, in another aspect, a power toolincluding a housing having a motor housing portion and a mount, a motorlocated within the motor housing portion, a spindle configured to rotateabout a rotational axis in response to torque received from the motor,and a handle holder selectively securable to the mount in a plurality ofdifferent rotational orientations about the rotational axis. The handleholder includes a first mounting point, and the housing includes asecond mounting point. The power tool also includes an auxiliary handleselectively attachable to each of the first mounting point and thesecond mounting point.

Other features and aspects of the invention will become apparent byconsideration of the following detailed description and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a core drill in accordance with anembodiment of the invention.

FIG. 2 is a cross-sectional view of the core drill of FIG. 1.

FIG. 3 is a plan view of a drive assembly of the core drill of FIG. 1.

FIG. 4 is a partially exploded view of the drive assembly of FIG. 3.

FIG. 5A is a partially exploded view illustrating a band assembly of thecore drill of FIG. 1.

FIG. 5B is a partially exploded view illustrating an auxiliary handle ofthe core drill of FIG. 1.

FIG. 6 is a top view of the core drill of FIG. 1 illustrating theauxiliary handle in an alternative position.

FIG. 7 is a perspective view of a portion of the core drill of FIG. 1.

FIG. 8 is a cross-sectional view of a portion of the core drill of FIG.1.

FIG. 9 is a schematic view illustrating a fluid delivery system of thecore drill of FIG. 1.

FIG. 10 is a cross-sectional view illustrating a cooling air path of thecore drill of FIG. 1.

FIG. 11 is a perspective view of a portion of the core drill of FIG. 1.

FIG. 12 is a cross-sectional view illustrating an intake opening of thecore drill of FIG. 1.

FIG. 13A is a perspective view illustrating an exhaust opening of thecore drill of FIG. 1.

FIG. 13B is a cross-sectional view illustrating the exhaust opening ofFIG. 13A.

FIG. 14 is an exploded view of a front portion of a core drill inaccordance with another embodiment of the invention, illustrating across-section of an auxiliary handle of the core drill.

FIG. 15 is a cross-sectional view taken along line 15-15 in FIG. 14.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate a rotary power tool, which is a core drill 10in the illustrated embodiment. The core drill 10 includes a housing 14,a first or rear handle 16, and a second or auxiliary handle 18. Agenerally D-shaped gap 19 is defined between the rear handle 16 and thehousing 14. The gap 19 provides clearance for a user's fingers when theuser grasps the rear handle 16. In the illustrated embodiment, the rearhandle 16 includes a base portion 16 a at its lower end that extends tothe housing 14. As such, the gap 19 is an aperture that is fully boundedabout its perimeter by the rear handle 16, the base portion 16 a, andthe housing 14. In other embodiments, the base portion 16 a may notconnect to the housing 14.

The illustrated housing 14 is a clamshell housing having left and rightcooperating halves 14 a, 14 b and includes a motor housing portion 20and a drive housing 22 (FIG. 1). An electric motor 24 is mounted in themotor housing portion 20 (FIG. 2). In the illustrated embodiment, themotor 24 is a brushless direct current motor; however, in otherembodiments, the core drill 10 may include other types of motors. Theillustrated core drill 10 is cordless and includes a battery 28 thatprovides power to the motor 24. The battery 28 is removably coupled to abattery receptacle 30, which is located underneath the motor housingportion 20 in the illustrated embodiment. In other embodiments, the coredrill 10 may be a corded tool configured to receive power from a walloutlet or other remote power source. A trigger 31 is provided on therear handle 16 and energizes the motor 24 when depressed by a user.

With continued reference to FIG. 2, the battery 28 is a power toolbattery pack and includes a battery housing 32 and a plurality ofrechargeable battery cells 34 disposed within the housing 32. Thebattery cells 34 are preferably lithium-based battery cells but canalternatively have any other suitable chemistry. In the illustratedembodiment, the battery 28 has a nominal output voltage of about 80V. Inother embodiments, the battery 28 can have a different nominal voltage,such as, for example, 36V, 40V, 72V, between 36V and about 80V, orgreater than 40V.

The core drill 10 further includes a spindle 36 rotatable about arotational axis 38 in response to receiving torque from the motor 24(FIG. 2). A tool bit (not shown) can be coupled to the spindle 36 forco-rotation with the spindle 36 to perform work (e.g., drilling) on aworkpiece. A drive assembly 40 is disposed within the drive housing 22to transmit torque from an output shaft 42 of the motor 24 to thespindle 36.

With reference to FIGS. 3 and 4, the illustrated drive assembly 40includes a multi-speed transmission 44. The transmission 44 includes twogear stages 46, 50 respectively referred to herein as a first gear stage46 and a second gear stage 50; however, the terms first and second donot imply any spatial or mechanical relationship of the gear stages 46,50 relative to each other, to the motor 24, or to the spindle 36. In theillustrated embodiment of the transmission 44, the first gear stage 46includes an intermediate shaft 54 and a helical gear 58 coupled forco-rotation with the intermediate shaft 54. The helical gear 58 may becoupled to the intermediate shaft 54 in any of a number of differentways (e.g., by using a key and keyway arrangement, an interference fit,a spline-fit, etc.). In the illustrated embodiment, the helical gear 58includes an integrated clutch mechanism (not shown) for limiting theamount of torque transferrable between the motor 24 and the spindle 36.In other embodiments, other clutch mechanisms may be employed at anyposition along the drive assembly 40. Alternatively, the motor 24 may beprovided with an electronic clutch, or the drive assembly 40 may notinclude a clutch.

The helical gear 58 includes a plurality of teeth meshed withcorresponding teeth on a pinion 62 of the motor output shaft 42 fortransmitting torque from the output shaft 42 to the intermediate shaft54. In the illustrated embodiment, the helical gear 58 has a greaternumber of teeth than the pinion 62 in order to provide a rotationalspeed reduction and corresponding torque increase from motor outputshaft 42 to the intermediate shaft 54. The first gear stage 46 furtherincludes a first driving gear 66 and a second driving gear 70 axiallyoffset from the first driving gear 66. The first and second drivinggears 66, 70 may be integrally formed with the intermediate shaft 54 ormay be formed separately and coupled to the intermediate shaft 54 forco-rotation therewith in any of a number of different ways.

The second gear stage 50 includes first and second driven gears 74, 78and a hub 82 supported on the spindle 36 between the driven gears 74,78. In the illustrated embodiment, the hub 82 is coupled for co-rotationwith the spindle 36 using a spline-fit, but the hub 82 may be coupled tothe spindle 36 in other ways. The first driven gear 74 and the seconddriven gear 78 are axially fixed on the spindle 36 (e.g., via one ormore snap rings, shoulders, or other inter-engaging features) with thehub 82 acting as a spacer between the two driven gears 74, 78. Thespindle 36 extends through a cylindrical bore in each of the respectivedriven gears 74, 78 such that the driven gears 74, 78 are rotatablerelative to the spindle 36.

The first and second driving gears 66, 70 each include external teeththat are continuously meshed with external teeth of respective first andsecond driven gears 74, 78. In the illustrated embodiment, the firstdriving gear 66 and the first driven gear 74 are sized to provide afirst gear reduction, and the second driving gear 70 and the seconddriven gear 78 are sized to provide a second gear reduction greater thanthe first gear reduction. Accordingly, during operation, the firstdriven gear 74 rotates at a relatively high speed and low torque, andthe second driven gear 78 rotates at a relatively low speed and hightorque.

Referring to FIG. 4, the hub 82 includes a plurality ofaxially-extending external splines 86. The first driven gear 74 includessplined portion 90 adjacent the hub 82 that has a correspondingplurality of external splines. Similarly, the second driven gear 78 alsoincludes a splined portion 94 adjacent the hub 82 that has acorresponding plurality of external splines. The transmission 44 furtherincludes a collar 98 having a plurality of internal splines 102 thatreceive the external splines 86 of the hub 82 to couple the collar 98for co-rotation with the hub 82. The hub 82, the driven gears 74, 78,and the collar 98 can be made of powdered metal using a suitableprocess, such as a compaction and sintering process. Alternatively, oneor more of the hub 82, the driven gears 74, 78, and the collar 98 can bemade of other materials and by other processes, such as machining,die-casting, and the like. As described in further detail below, thecollar 98 is shiftable along the spindle 36 to selectively interconnectthe splines 86 on the hub with the splined portions 90, 94 of therespective driven gears 74, 78. In the illustrated embodiment, thesplines on the driven gears 74, 78 each have a narrower width than thesplines 86 on the hub 82. This difference in width provides clearance tofacilitate shifting of the collar.

The transmission 44 further includes a shift mechanism 104 operable tomove the collar 98 between a first position (not shown), in which thecollar 98 engages the splined portion 90 of the first driven gear 74 andthe hub 82 to couple the first driven gear 74 and the hub 82 forco-rotation, and a second position (FIG. 3), in which the collar 98engages the splined portion 94 of the second driven gear 78 and the hub82 to couple the second driven gear 78 and the hub 82 for co-rotation.In the illustrated embodiment of the transmission 44, the shiftmechanism 104 includes a pair of linearly movable, nested brackets 106,110 for shifting the collar 98 between the first and second positions. Abiasing member 114 (e.g., a coil spring) is disposed between the twobrackets 106, 110. The brackets 106, 110 and the biasing member 114 aremovable together along a rod 120 in response to manual manipulation ofan actuator knob 124. The actuator knob 124 includes an eccentric pin(not shown) that is received within a gap 132 between the shift brackets106, 110 (FIG. 4). As such, rotation of the actuator knob 124 causeslinear movement of the brackets 106, 110 (and therefore, the collar 98).Alternatively, the shift mechanism 104 may be configured in any of anumber of different ways for displacing the collar 98 between the firstand second positions.

In operation, when the transmission 44 is configured in a high speed,low torque mode, the shift mechanism 104 and the collar 98 are shiftedto the first position, thereby coupling the first driven gear 74 to thehub 82 for co-rotation. As such, the spindle 36, the hub 82, and thefirst driven gear 74 all co-rotate together at a relatively high speed.Because the second driven gear 78 is continuously meshed with the seconddriving gear 98, the second driven gear 78 continues to rotate at arelatively slow speed (i.e., slower than the rotational speed of thespindle 22), and the spindle 36 rotates within the second driven gear78. When the transmission 44 is configured in a low speed, high torquemode, the shift mechanism 104 and the collar 98 are shifted to thesecond position (FIG. 3), thereby coupling the second driven gear 78 tothe hub 82 for co-rotation. As such, the spindle 22, the hub 82, and thesecond driven gear 78 all co-rotate together at a relatively low speed.Because the first driven gear 74 remains continuously meshed with thefirst driving gear 94, the first driven gear 74 continues to rotate at arelatively high speed (i.e., faster than the rotational speed of thespindle 22) and rotates relative to the spindle 22.

To shift the transmission 44 from the high speed, low torque mode to thelow speed, high torque mode, a user begins rotating the actuator knob124. As the actuator knob 124 rotates, the eccentric pin bears againstthe second bracket 110 which, in turn, pushes against the biasing member114 to move the first bracket 106 and the collar 98 toward the secondposition (FIG. 3). The collar 98 then enters a neutral position (notshown), midway between the first position and the second position. Inthe neutral position, the collar 98 is disengaged from both the firstand second driven gears 74, 78 such that no torque is transferred fromthe driven gears 74, 78 to the hub 82 (and therefore, the spindle 36).If the user continues to rotate the actuator knob 124 and the internalsplines 102 of the collar 98 are not yet aligned with the splines of thesecond driven gear 78, the biasing member 114 is compressed between thebrackets 106, 110. Once the respective splines are aligned, the biasingmember 114 urges the first bracket 106 and the collar 98 into the secondposition. Accordingly, the biasing member 114 permits a delay betweenrotation of the actuator knob 124 and engagement of the collar 98 withthe second driven gear 78. Similarly, when shifting the transmission 44from the low speed, high torque mode to the high speed, low torque mode,the biasing member 114 permits a delay between rotation of the actuatorknob 124 and engagement of the collar 98 with the first driven gear 74.

The drive assembly 40 of the core drill 10 advantageously provides forquiet operation. The core drill 10 was tested during no-load operation(i.e. without a tool bit coupled to the spindle 36). Sound pressure datawas measured using five microphones surrounding the core drill 10, eachpositioned at a distance of one meter from the core drill 10. Thesemeasurements were then averaged. In the illustrated embodiment, the coredrill 10 produces an average sound pressure at a distance of one meterfrom the drill 10 of 80.0 decibels (dBa) when operating in the highspeed, low torque mode. The core drill 10 produces an average soundpressure at a distance of one meter from the drill 10 of 80.4 dBa whenoperating in the low speed, high torque mode. Thus, regardless of speed,during no-load operation, the core drill 10 produces an average soundpressure less than 81 dBa at a distance of one meter from the drill 10.

With reference to FIG. 5A, the drive housing 22 includes a cylindricalmount 150 extending forward along the spindle 36. A handle holder orband assembly 154 is coupled to the mount 150. In the illustratedembodiment, the band assembly 154 includes an adjustable band 158 and agenerally Y-shaped base 162. The auxiliary handle 18 is removablyattached to the base 162. The band assembly 154 may be selectivelyrotatable about the rotational axis 38 of the spindle 36 to allow theauxiliary handle 18 to be positioned in a variety of differentorientations. In the illustrated embodiment, the mount 150 includes aplurality of teeth or undulations 166 that are engageable withcorresponding teeth or undulations 170 on the base 162 to define avariety of discrete, angular positions of the band assembly 154 (and theauxiliary handle 18).

With reference to FIG. 5B, the auxiliary handle 18 includes a threadedshank 174 that is received within a threaded bore (not shown) in theunderside of the base 162 to removably couple the auxiliary handle 18 tothe band assembly 154. In the illustrated embodiment, the housing 14includes a mounting portion 178 situated between the drive housing 22and the motor housing portion 20. In some embodiments, the mountingportion 178 may be integrally formed with the drive housing 22, and inother embodiments, the mounting portion 178 may be integrally formedwith the motor housing portion 20. Alternatively, the mounting portion178 can be a separate component assembled together with the housing 14.

Referring also to FIG. 6, the mounting portion 178 includes a firstthreaded bore 182 (FIG. 5B) and a second threaded bore 186 (FIG. 6)opposite the first threaded bore 182. Each of the bores 182, 186 acts asa mounting point for receiving the threaded shank 174 of the auxiliaryhandle 18 to directly couple the auxiliary handle 18 to the mountingportion 178. This advantageously provides a variety of differentplacement options for the auxiliary handle 18. In some embodiments, thecore drill 10 may include only one of the first and second bores 182,186, or may include more than two bores. Alternatively, the bores 182,186 may be omitted. The illustrated first and second bores 182, 186extend inwardly from opposite lateral sides of the core drill 10, in adirection generally perpendicular to the rotational axis 38 of thespindle 36. Accordingly, when the auxiliary handle 18 is attached to thefirst bore 182 or the second bore 186, the auxiliary handle 18 extendsoutwardly from the left side or the right side of the core drill 10. Inother embodiments, one or both of the first and second bores 182, 186may extend at an oblique angle with the rotational axis 38. In someembodiments, the first and second bores 182, 186 are coaxial and definean axis 190 that intersects the rotational axis 38. In otherembodiments, the axis 190 can be offset above or below the rotationalaxis 38. In yet other embodiments, the first and second bores 182, 186may not be coaxial. In the illustrated embodiment, the axis 190 isoffset from the band assembly 154 along the rotational axis 38 such thatthe band assembly 154 and the bores 182, 186 provide at least twodifferent mounting locations for the auxiliary handle 18 along thelength of the core drill 10.

With reference to FIGS. 7-9, the illustrated core drill 10 furtherincludes a fluid distribution system 200. The fluid distribution system200 includes a first connector 204 and a supply line 208 (FIG. 9) thatcan be attached to the first connector 204 to provide fluid such aswater to the fluid distribution system 200 from an external source (notshown). A delivery line 212 extends from a second connector 216 (FIG. 7)to the spindle 36, and a valve 220 is disposed between the first andsecond connectors 204, 216 to regulate fluid flow from the supply line208 to the delivery line 212. The delivery line 212 may extend entirelyor partially through the interior of the housing 14, or may extendentirely or partially along the exterior of the housing 14. Theillustrated first and second connectors 204, 216 are each barb fittings;however, other suitable types of hose fittings may be used. In theillustrated embodiment, the first and second connectors 204, 216 arerecessed into the housing 14 to provide protection for the connectors204 216.

Referring to FIG. 7, the valve 220 includes a valve housing 224, a valvebody 228 that is rotatable relative to the valve housing 224 about anaxis 232, and an actuator lever 236 extending from the valve body 228.In other embodiments, the valve 220 may have other components orconfigurations. The valve 220 is positioned proximate the rear handle 16and preferably within the gap 19 between the rear handle 16 and thehousing 14. As such, a user may grip the rear handle 16, depress thetrigger 31, and actuate the valve 220 (by manipulating the actuatorlever 236) with the same hand. In the illustrated embodiment, the valve220 is centered along the width of the core drill 10 such that the axis232 is coplanar with the rotational axis 38 of the spindle 36. Thisadvantageously allows the user to actuate the valve 220 regardless ofwhich of the user's hands is used to grasp the rear handle 16. In otherembodiments, the valve 220 may be positioned off center, proximate theleft side or the right side of the core drill 10.

With reference to FIG. 8, the downstream end of the delivery line 212can be attached to a third connector 240 located on the drive housing 22adjacent the band assembly 154. The third connector 240 fluidlycommunicates with an annular volume 244 surrounding the spindle 36. Theannular volume 244 is bounded by first and second spaced annular seals248 a, 248 b. The spindle 36 includes a plurality of radially extendingapertures 252 that fluidly communicate a hollow interior 256 of thespindle 36 with the annular volume 244. As such, fluid that flowsthrough the delivery line 212 and into the annular volume 244 can enterthe spindle 36 through the apertures 252. The fluid can then flowthrough the hollow interior 256 of the spindle 36, and subsequentlythrough a core bit attached to the spindle 36, for cooling, lubrication,and dust abatement.

Referring to FIG. 10, operation of the motor 24 is governed by a motorcontrol system including a printed circuit board (“PCB”) 300 thatincludes power electronics such as switching elements and the like. Theillustrated core drill 10 includes a fan 304 coupled to the motor outputshaft 42 that generates a cooling airflow through the housing 14 toremove heat from the PCB 300 and/or any other heat-generatingcomponents.

The illustrated housing includes left and right side walls 308, 312(FIG. 6) that extend generally parallel to the rotational axis 38 of thespindle 36, and a rear wall 316 (FIG. 11) that opposes the rear handle16. Left and right angled walls 320, 324 extend between the respectiveside walls 308, 312 and the rear wall 316, and the angled walls 320, 324are oriented inward toward the center of the core drill 10 at an obliqueangle. In the illustrated embodiment, the angled walls 320, 324 and therear wall 316 each include a plurality of segments oriented at differentangles; however in other embodiments, the angled walls 320, 324 and therear wall 316 may be substantially planar, curved, or include any numberof segments or contours.

The housing 14 includes a plurality of intake openings 328 located onthe angled walls 320, 324 (FIG. 11). The position of the intake openings328 on the angled walls 320, 324 advantageously helps shield them fromfluid spray, dust, and debris that may be present during operation ofthe core drill 10. In the illustrated embodiment, a deflector 332 isdisposed adjacent each of the intake openings 328 to direct fluid awayfrom the openings 328. In other embodiments, the intake openings 328 maybe arranged and positioned differently. Additionally, the core drill 10may draw intake air from other locations.

The housing 14 further includes exhaust openings 336 located on the leftand right sides 308, 312 of the housing 14. The exhaust openings 336open downward with reference to the orientation of the core drill 10illustrated in FIG. 11 to inhibit fluid, dust, and debris from enteringthe housing through the exhaust openings 336. A scoop-shaped deflector340 extends downwardly from the exhaust openings 336 to further inhibitthe ingress of fluid, dust and debris. (FIG. 13). The scoop-shapeddeflector 340 terminates at an angled surface 344 that is oriented todirect fluid, dust, and debris away from the exhaust openings 336 whenthe core drill 10 is used in a vertical drilling orientation. In otherembodiments, the exhaust openings 336 may be arranged and positioneddifferently. Additionally, the core drill 10 may exhaust air from otherlocations.

During operation, the fan 304 draws cooling air into the housing 14through the intake openings along a cooling air path 348 (FIG. 10). Theair drawn through the air intake openings 328 is routed upwardly by awall 352. Any fluid that enters the housing 14 through the intakeopenings 328 will fall to the bottom of the housing 14, where it canexit through one or more drain orifices (not shown). The cooling airthen flows along a cooling path 356 and over a finned heat sink 360 tocool the PCB 300. After passing over the heat sink 360, the air canenter the motor housing portion 20, cooling the motor 24 before beingdischarged through the exhaust openings 336.

FIGS. 14-15 illustrate portions of a core drill 410 according to anotherembodiment. The core drill 410 is similar to the core drill 10 describedabove with reference to FIGS. 1-13B. Accordingly the followingdescription focuses only on differences between the core drill 410 andthe core drill 10. In addition, features and elements of the core drill410 corresponding with features and elements of the core drill 10 aregiven like reference numbers plus ‘400’.

Referring to FIG. 14, the core drill 410 includes a drive housing 422and a handle holder 554 coupled to a mount 550 that extends from a frontend of the drive housing 422. The handle holder 554 includes an aperture557 sized and shaped receive the mount 550 such that the handle holder554 can be slid onto the mount 550. In the illustrated embodiment, themount 550 and the aperture 557 are cylindrical, but the mount 550 andthe aperture 557 may alternatively define other cooperating shapes.

The handle holder 554 further includes a locking element 559, a nut 561,and a spring 563 disposed between the nut 561 and the locking element559. The locking element 559 includes teeth 565 that project radiallyinward from an inner periphery of the aperture 557. The teeth 565 areengageable with corresponding teeth or undulations 566 on the mount 550to retain the handle holder 554 in a particular rotational position onthe mount 550. The locking element 559 is retractable (i.e. displaceabletoward the nut 561), against the biasing force of the spring 563, topermit the handle holder 554 to rotate about the mount 550 to differentrotational positions.

With continued reference to FIG. 14, the core drill 410 includes anauxiliary handle 418 with a threaded shank 574 that is received withinthe nut 561 to removably couple the auxiliary handle 418 to the handleholder 554. A distal end of the threaded shank 574 is engageable withthe locking element 559 when the auxiliary handle 418 is rotatedrelative to the handle holder 554 in a tightening direction 567, whichprevents the locking element 559 from retracting. The auxiliary handle418 is thus rotatable in the tightening direction 567 to secure thehandle holder 554 (and the auxiliary handle 418) in a particular angularposition on the mount 550. In addition, further rotation of the threadedshank 574 in the tightening direction 567 may exert a clamping force themount 550 via the locking element 559 to axially secure the handleholder 554 and the auxiliary handle 418 on the mount 550.

Conversely, the auxiliary handle 418 is rotatable in a looseningdirection 569 opposite the tightening direction 567, which, due to thethreaded engagement between the shank 574 and the nut 561, displaces thethreaded shank 574 away from the locking element 559. If sufficientforce is then applied to the auxiliary handle 418, the engagementbetween the undulations 566 and the teeth 565 causes the locking element559 to retract into the handle holder 554 and permit rotation of thehandle 418 and handle holder 554 about the mount 550. Further rotationof the auxiliary handle 418 in the loosening direction 569 may decouplethe handle 418 from the handle holder 554. An operator may then elect toattach the auxiliary handle 418 to other mounting points on the coredrill 410 (such as on the mounting portion 178 described above withreference to FIG. 6).

With reference to FIG. 15, the illustrated core drill 410 includes a bitholder 571 on the spindle 436 and a bit 573 coupled to the bit holder571. The bit holder 571 includes a threaded end portion 575 of thespindle 436 and a backer flange 577 surrounding the spindle 436. The bit573 includes internal threads 579 that engage the threaded end portion575 to couple the bit 573 to the bit holder 571. The backer flange 577has a front portion 581 and a rear portion 583 engaged against ashoulder 585 formed on the spindle. The rear portion 583 has anaxially-extending wall 587 that at least partially surrounds an outerperiphery of the front portion 581. In the illustrated embodiment, athin disc of low-friction material 589, such as Teflon paper, isdisposed axially between the front portion 581 and the rear portion 583of the backer flange 577.

In use, to secure the bit 573 to the bit holder 571, an operator engagesthe threaded portion 575 of the bit holder 571 with the internal threads579 on the bit 573, then rotates the bit 573 in a tightening direction591 to advance the bit 573 toward the backer flange 577. Once a rear end593 of the bit 573 engages the front portion 581 of the backer flange577, the operator continues to rotate the bit 573 in the tighteningdirection 591, which develops an axial force on the flange 577 and acorresponding reaction force on the threads 575, 579. This reactionforce increases friction between the threads 575, 579 and inhibits thebit 573 from loosening unintentionally. In the illustrated embodiment,the bit 573 includes flats 595 that allow the operator to applyadditional torque on the bit 573 in the tightening direction 591 using awrench, for example.

To loosen the bit 573, the operator rotates the bit 573 in a looseningdirection 597. The disc of low friction material 589 between the frontportion 581 and the rear portion 583 of the backer flange 577 allows thefront portion 581 to rotate relative to the rear portion 583 more easilyunder the axial load applied on the front portion 581 by the bit 573. Assuch, the rear end 593 of the bit 573 does not bind on the backer flange577, which facilitates removal of the bit 573.

With continued reference to FIG. 15, in the illustrated embodiment, thebit 573 is an adapter bit. As such, the bit 573 includes a second bitholder 599 having a front threaded portion 601. The front threadedportion 601 of the second bit holder 599 has a different (e.g., smaller)diameter than the threaded portion 575 of the bit holder 571. Thus, thecore drill 410 is adaptable for use with different tool bits using asingle spindle 436. For example, the threaded portion 575 of the bitholder 571 may be sized to receive a wet core bit (not shown) intendedfor use with a fluid distribution system of the core drill 410 (e.g.,the fluid distribution system 200). The wet core bit may be attached tothe bit holder 571 in the same manner as the adapter bit 573 describedabove. The front threaded portion 601 of the second bit holder 599 maybe sized to receive a dry core bit (not shown) intended for use withoutoperating the fluid distribution system.

Like the bit holder 571, the second bit holder 599 includes a backerflange 603. The backer flange 603 is coupled to the adapter bit 573 by aretaining ring 605. A thin disc of low-friction material 607, such asTeflon paper, is disposed axially between the backer flange 603 and ashoulder 608 formed at a base of the front threaded portion 601.

In use, to secure a bit (e.g., the dry core bit) to the spindle 436 viathe second bit holder 599, an operator engages the front threadedportion 601 with internal threads on the bit, then rotates the bit in atightening direction 591 to advance the bit toward the backer flange603. Once a rear end of the bit engages a front side 609 of the backerflange 603, the operator continues to rotate the bit in the tighteningdirection 591, which develops an axial force on the flange 603 and acorresponding reaction force on the threads 601. This reaction forceincreases friction between the threads 601 and the bit, and inhibits thebit from loosening unintentionally. To loosen the bit, the operatorrotates the bit in the loosening direction 597. The disc of low frictionmaterial 607 between the backer flange 603 and the shoulder 608 allowsthe backer flange 603 to rotate relative to the remainder of the adapterbit 573 more easily under the axial load applied on the front side 609by the bit. As such, the rear end of the bit does not bind on the backerflange 603, which facilitates removal of the bit.

Various features of the invention are set forth in the following claims.

What is claimed is:
 1. A power tool, comprising: a housing including amotor housing portion, a drive housing, and a mounting portion betweenthe motor housing portion and the drive housing; a motor located withinthe motor housing portion; a spindle configured to rotate about arotational axis in response to torque received from the motor; a handleholder coupled to the drive housing, the handle holder defining a firstmounting point, and the mounting portion defining a second mountingpoint; and an auxiliary handle selectively attachable to each of thefirst and second mounting points, wherein the first mounting point islocated at a first position along the rotational axis, and the secondmounting point is located at a second position offset from the firstposition in a direction along the rotational axis.
 2. The power tool ofclaim 1, wherein the auxiliary handle includes a threaded shank, andwherein each of the first and second mounting points includes a threadedbore configured to receive the threaded shank.
 3. The power tool ofclaim 1, wherein the handle holder is selectively rotatable relative tothe drive housing about the rotational axis between a plurality ofrotational positions.
 4. The power tool of claim 3, wherein the handleholder includes a tooth.
 5. The power tool of claim 4, wherein the toothis engageable with a plurality of teeth on the housing to retain thehandle holder in the plurality of rotational positions.
 6. The powertool of claim 1, wherein the mounting portion defines a third mountingpoint, and wherein the auxiliary handle is selectively attachable to thethird mounting point.
 7. The power tool of claim 6, wherein the thirdmounting point and the second mounting point are positioned on oppositesides of the rotational axis.
 8. The power tool of claim 6, wherein theauxiliary handle includes a threaded shank, and wherein each of thefirst, second, and third mounting points includes a threaded boreconfigured to receive the threaded shank.
 9. The power tool of claim 8,wherein the threaded bore of the second mounting point and the threadedbore of the third mounting point extend inwardly from opposite sides ofthe mounting portion.
 10. A power tool, comprising: a housing includinga motor housing portion, a drive housing, and a mounting portion betweenthe motor housing portion and the drive housing; a motor located withinthe motor housing portion; a spindle configured to rotate about arotational axis in response to torque received from the motor; atransmission at least partially disposed within the drive housing, thetransmission configured to transmit torque from the motor to thespindle; and an auxiliary handle selectively attachable to the housingat each of a first mounting point, a second mounting point, and a thirdmounting point, wherein at least one of a group consisting of the firstmounting point, the second mounting point, and the third mounting pointis located on the mounting portion.
 11. The power tool of claim 10,wherein the auxiliary handle includes a threaded shank, and wherein eachof the first, second, and third mounting points includes a threaded boreconfigured to receive the threaded shank.
 12. The power tool of claim11, wherein the threaded bore of the second mounting point and thethreaded bore of the third mounting point extend inwardly from oppositesides of the mounting portion.
 13. The power tool of claim 10, furthercomprising a handle holder coupled to the drive housing, the handleholder defining the first mounting point.
 14. The power tool of claim13, wherein the first mounting point is located at a first positionalong the rotational axis, the second mounting point is located at asecond position offset from the first position in a direction along therotational axis, and the third mounting point is located at a thirdposition offset from the first position in the direction along therotational axis.
 15. The power tool of claim 10, wherein the firstmounting point is selectively rotatable about the rotational axisrelative to the housing.
 16. A power tool, comprising: a housingincluding a motor housing portion and a mount; a motor located withinthe motor housing portion; a spindle configured to rotate about arotational axis in response to torque received from the motor; a handleholder selectively securable to the mount in a plurality of differentrotational orientations about the rotational axis, wherein the handleholder includes a first mounting point, and the housing includes asecond mounting point; and an auxiliary handle selectively attachable toeach of the first mounting point and the second mounting point.
 17. Thepower tool of claim 16, wherein the first mounting point is located at afirst position along the rotational axis, and the second mounting pointis located at a second position offset from the first position in adirection along the rotational axis.
 18. The power tool of claim 16,wherein the auxiliary handle is rotatable in a loosening direction topermit adjustment of the handle holder between the plurality ofrotational orientations, and wherein the auxiliary handle is rotatablein a tightening direction to secure the handle holder in a selected oneof the plurality of rotational orientations.
 19. The power tool of claim18, wherein the auxiliary handle includes a threaded shank, wherein thehandle holder includes a locking element, and wherein rotation of theauxiliary handle in the tightening direction engages the threaded shankagainst the locking element.
 20. The power tool of claim 19, wherein thelocking element is biased into engagement with the mount.